fix(settings): make ConfigCheckService use Files.exist IQSS#9662

With Files.notExist if some folder does not have the "execute"
attribute, it cannot detect a folder does not exist.
Inverting the Files.exists call solves the problem.

Also adding tests for the business logic.

src/main/java/edu/harvard/iq/dataverse/settings/ConfigCheckService.java

@@ -49,7 +49,7 @@ public boolean checkSystemDirectories() {
 
         boolean success = true;
         for (Path path : paths.keySet()) {
-            if (Files.notExists(path)) {
+            if (! Files.exists(path)) {
                 try {
                     Files.createDirectories(path);
                 } catch (IOException e) {

src/test/java/edu/harvard/iq/dataverse/settings/ConfigCheckServiceTest.java

@@ -0,0 +1,92 @@
+package edu.harvard.iq.dataverse.settings;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Assumptions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Set;
+
+import static java.nio.file.attribute.PosixFilePermission.GROUP_READ;
+import static java.nio.file.attribute.PosixFilePermission.OWNER_READ;
+
+class ConfigCheckServiceTest {
+
+    @Nested
+    class TestDirNotWritable {
+        @TempDir
+        Path testDir;
+
+        private String oldUploadDirSetting;
+
+        @BeforeEach
+        void setUp() throws IOException {
+            Files.setPosixFilePermissions(this.testDir, Set.of(OWNER_READ, GROUP_READ));
+
+            // TODO: This is a workaround until PR #9273 is merged, providing the ability to lookup values for
+            //       @JvmSetting from static methods. Should be deleted.
+            this.oldUploadDirSetting = System.getProperty(JvmSettings.UPLOADS_DIRECTORY.getScopedKey());
+            System.setProperty(JvmSettings.UPLOADS_DIRECTORY.getScopedKey(), this.testDir.toString());
+        }
+
+        @AfterEach
+        void tearDown() {
+            // TODO: This is a workaround until PR #9273 is merged, providing the ability to lookup values for
+            //       @JvmSetting from static methods. Should be deleted.
+            if (this.oldUploadDirSetting != null)
+                System.setProperty(JvmSettings.UPLOADS_DIRECTORY.getScopedKey(), this.oldUploadDirSetting);
+        }
+
+        @Test
+        void writeCheckFails() {
+            Assumptions.assumeTrue(Files.exists(this.testDir));
+
+            ConfigCheckService sut = new ConfigCheckService();
+            Assertions.assertFalse(sut.checkSystemDirectories());
+        }
+    }
+
+    @Nested
+    class TestDirNotExistent {
+        @TempDir
+        Path testDir;
+        String subFolder = "foobar";
+
+        String oldUploadDirSetting;
+
+        @BeforeEach
+        void setUp() throws IOException {
+            // Make test dir not writeable, so the subfolder cannot be created
+            Files.setPosixFilePermissions(this.testDir, Set.of(OWNER_READ, GROUP_READ));
+
+            // TODO: This is a workaround until PR #9273 is merged, providing the ability to lookup values for
+            //       @JvmSetting from static methods. Should be deleted.
+            oldUploadDirSetting = System.getProperty(JvmSettings.UPLOADS_DIRECTORY.getScopedKey());
+            System.setProperty(JvmSettings.UPLOADS_DIRECTORY.getScopedKey(), this.testDir.resolve(this.subFolder).toString());
+        }
+
+        @AfterEach
+        void tearDown() {
+            // TODO: This is a workaround until PR #9273 is merged, providing the ability to lookup values for
+            //       @JvmSetting from static methods. Should be deleted.
+            if (this.oldUploadDirSetting != null)
+                System.setProperty(JvmSettings.UPLOADS_DIRECTORY.getScopedKey(), this.oldUploadDirSetting);
+        }
+
+        @Test
+        void mkdirFails() {
+            Assumptions.assumeTrue(Files.exists(this.testDir));
+            Assumptions.assumeFalse(Files.exists(this.testDir.resolve(this.subFolder)));
+
+            ConfigCheckService sut = new ConfigCheckService();
+            Assertions.assertFalse(sut.checkSystemDirectories());
+        }
+    }
+
+}